This is a problem that dual mode decoders have from time to time if DC mode is left on.
What happens is on power up the decoder will check for a valid DCC signal. If the decoder doesn't see DCC it thinks it's a DC layout and switches to that mode. What happens is that if there is a quick short in the track for whatever reason the voltage drops then comes back on. The decoder sees this as a start up and looks for DCC. The DCC signal sometimes doesn't recover right away and the decoder thinks it DC. Now the decoder switches to DC and guess what? The full track voltage is available to it. As a result the loco runs max speed until it hits something or you grab it. I learned it the hard way too.
Turning off DC mode prevents the decoder from doing the DCC check and always assumes it is present.
Springfield PA
I did the reset using CV8, set to 8 and then reset the address to 12 using 2 digit address. So far everything is OK. I left the engine on the tracks for about 1 hour today and it stayed put!. Thanks for all your input.
Bob
Life is what happens while you are making other plans!
I did a CV-RD and it verified 002 as the value. I changed the address when first used to a 2 digit address. I have 4 other Bachmann DCC On-Board engines and this is the only one that does this. If this is a problem with Bachmann decoders (Tsunami or ?) why don't they fix the problem rather that sustaing a bad image for their products?
BTW, thanks for the CV29 calculator. I used the same table to figure out what to set mine at. The calculator won't work with Windows 7 though.
A value of 2 should have done the trick if you're not using a long address. It's possible that the program change didn't take effect. Try programming it on the main.
Here's a cv29 calculator as well
http://www.2mm.org.uk/articles/cv29%20calculator.htm
If you have the decoder set to a long address, CV29 should be 34.
I checked the CV29 value and it was 6. I changed it to 2, according to the literature on these settings. It indicated 4 bits for analog or digital and by closing that it left 2 as the setting. I changed it and put it back on the layout. Not even 15 minutes later it took off in reverse and before I could stop it it rammed four cars off the track. I removed the engine and if I can't get this resolved, I may just replace it with a NCE decoder.
I can't comment about that variant of Tsunami, but it should be a dual mode decoder that allows the user to operate the locomotive on either DC or DCC. The full-meal-deal Tsunamis are certainly like that.
I believe that you need to change the programmed value in CV29 from its current 38 to 34. The value of 34 makes the decoder inoperative/insensitive to DC current, and that is what it seems to be wanting to respond to. The Tsunamis are known for this litle heart-pounder.
Crandell
I just did a quick check with Bachmann's website and they show the CV29 settings as allowing DCC only or both DC/DCC. I will try to change the setting as see what happens. Thanks,
Most decoders as they come from the factory are set so the loco can run on DC as well as DCC. You can turn off the DC part. Sometimes that is the problem.
You will have to do some research to find out what CV it is unless you are using JMRI Decoder Pro like I am.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
I got a Bachmann DCC equipped GP38-2 for Christmas and it runs very well, even better than I expected. This past week it started to take off by itself, at full speed, while I was working with another loco. I have to shut the system down to stop it. This has happened about 4-5 times this past week. Any ideas what would cause it? How to correct it?